- 2 tablespoons unsalted butter, at room temperature
- 1 ounce blue cheese (1/4 cup)
- 1 pound purple- or red-skinned potatoes
- 3 tablespoons olive oil
- kosher salt and black pepper
- 1 1/2 pounds porterhouse steak (1 1/4 inches thick)
- 1 head butter lettuce or frisée, torn (6 cups)
- 1/2 cup halved cherry tomatoes
- 2 tablespoons red wine vinegar
- Heat oven to 425° F. Combine the butter and blue cheese in a small bowl; set aside.
- Place the potatoes in 1 inch of water in a microwave-safe dish, cover, and microwave on high until tender, 7 to 10 minutes. Drain and rinse with cold water to stop the cooking; halve.
- Heat 1 tablespoon of the oil in a large ovenproof skillet on high heat. Season the steak with 1 teaspoon each salt and pepper. Cook until browned, 3 to 4 minutes per side. Add the potatoes to the skillet with the steak. Transfer to oven and cook until an instant-read thermometer inserted in the thickest part of the steak registers 130° F for medium-rare, 7 to 10 minutes. Transfer the steak to a cutting board and top with half the blue cheese butter; let rest for 10 minutes before slicing against the grain.
- Toss the lettuce, tomatoes, vinegar, the remaining 2 tablespoons of oil, and ¼ teaspoon each salt and pepper in a large bowl.
- Serve the steak and potatoes with the remaining blue cheese butter alongside the salad.